Apertures, defined as discs containing one or more orifices, are used in numerous electron and other charged particulate beam systems. These apertures generally provide one of three functions. They serve either to:
1.) define the divergence angle of the electron beam from an emitting surface, which in turn determines the amount of aberrations ( i.e. spherical and chromatic) that the various beam controlling elements contribute to the focused particle beam,
2.) define the “object” bundle of electrons that subsequently becomes focused onto an image plane, or
3.) control the intensity of the charged particulate beam by varying the potential applied to the aperture.
Scientific, industrial, commercial, medical and military instruments employing electron and other particulate beams require beam defining and controlling apertures. Typical systems are: Scanning Electron Microscopes (SEM's), Transmission Electron Microscopes ( TEM's), Electron Beam Recorders ( EBR's), Electron Beam Lithography Systems ( EBL's )for generation of optical and X-Ray masks for Integrated Circuit (IC) fabrications, Direct Write Electron Exposure Systems for IC fabrication, Ion Beam and Implantation Systems and future Atomic Force Memory Systems.
The beam defining and controlling apertures used in these systems are made of metal, primarily platinum, molybdenum, tungsten, or metal foil on a backing. In many instruments the location of the aperture is such that it is bombarded by high current densities of high-energy particles. Such bombardment causes the apertures to become extremely hot. Under these conditions metal apertures can either melt down resulting in partial or total occlusion of the orifice or the orifice edges burn away thereby impairing the performance of the system. As the orifice size approaches 10 microns or less, the metals impose certain material restraints thereby limiting system performance. Among these are:                a.) Limitations on system throughput by having to limit beam power current to prevent metal aperture meltdown resulting in partial or total occlusion of the orifice.        b.) Limited life caused by gradual enlargement of the orifice with loss of spot size or feathering of orifice edges causing a “blooming” of the spot size.        
Further, metal aperture manufacturing technology cannot produce aperture orifices smaller than 10 microns with tolerances of typically +/−0.2 microns that can withstand high-density particulate bombardment. The feasibility of using gold coated, electrically non-conductive diamond as a base material has been demonstrated. However, the comparatively fragile gold coating reduces the dimensional integrity and useful lifetimes of these apertures.
The ability of metals to conduct heat diminishes with elevated temperatures. This results in erosion of the aperture thereby limiting service life. Further, metal foil is not capable of withstanding high-density particulate bombardment.
Accordingly, besides the objects and advantages of the apertures described in my above patent, several object and advantages of the present invention are:                a.) to provide an aperture with vastly superior thermal conductivity which will remove the instrument system restraints on present and emerging technology.        b.) to provide an aperture with superior thermal stability which will assure system integrity        c.) to provide an aperture that is chemically inert        d.) to provide an aperture that has excellent electrical conductivity        e.) to provide an aperture that can withstand high temperature cleaning without altering the critical orifice dimension        f.) to provide an aperture which will extend service life        g.) to provide an aperture which will yield high performance in ultrafine sizes below five microns        h.) to provide an aperture which can have manufacturing tolerances as fine as +/−0.2 microns ensuring system integrity        
Further objects and advantages are to provide an aperture which is directly interchangeable, forward and backward, with metal apertures presently in service; relatively inexpensive to manufacture and providing superior instrument performance applications and capabilities heretofore unattainable.
Specifically, electrically conductive synthetic diamond apertures have the following desirable features:                a.) Vastly Superior Thermal Conductivity compared to any metal.        
Diamond conducts heat faster and more reliably than any other material. A comparison of thermal conductivity for natural diamond, synthetic diamond, platinum, molybdenum and tungsten reveals the following:
W/CM° KDIAMOND (Type 1 - Natural Monocrystalline)@20° C. 9*@190° C.24*SYNTHETIC POLYCRYSTALLINE DIAMOND 7-12***PLATINUM 0.71*MOLYBDENUM@500° C. 1.22*@1000° C. 1.01*@1500° C. 0.82*TUNGSTEN @ 18° C. 1.47***KIRK OTHMER/ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY - 1978 **HANDBOOK OF CHEMISTRY AND PHYSICS 44th EDITION 1962-63 ***GENA SYSTEMS MARCH 1990                 b.) Superior Thermal Stability        
Diamond is a dimensionally stable material. Compared to most metals, its expansion and contraction rate is very low. For example, it expands and contracts only one third as much a tungsten. Because of this low thermal expansion rate, diamond provides superior dimensional stability at elevated temperatures (621.9 Proceedings—International Diamond Conf. 1969).                c.) Chemically Inert        
Diamond is virtually non-destructible.